IMPORTANCE: In recent decades, evidence-based psychotherapies to treat posttraumatic stress disorder (PTSD) have been developed with robust evidence bases. However, efficacy observed in clinical trials is not always directly applicable to clinical practice. OBJECTIVE: To estimate the percentage of patients in both military and veteran (hereafter milvet) and nonmilvet populations that lose their PTSD diagnosis after treatment. DATA SOURCES: We used the PTSD Repository to identify studies with adults with a DSM-IV/DSM-5 PTSD diagnosis based on a validated assessment. The repository, maintained by the US National Center for PTSD, is continually updated with randomized clinical trials and includes studies published from January 1988 on. STUDY SELECTION: For eligibility, PTSD had to be the primary treatment target, with psychotherapy applied as monotreatment. Eligible studies reported the number of participants who did not meet diagnostic criteria for PTSD posttreatment. When this review was initiated (October 2023), the repository contained 496 unique studies. Data analysis was completed from October 2023 to June 2024. DATA EXTRACTION AND SYNTHESIS: The repository follows Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guidelines and uses Cochrane Risk of Bias 2.0. We used mixed-effects logistic regression models to estimate diagnosis loss and incorporated milvet status and sex as covariates. MAIN OUTCOMES AND MEASURES: The primary outcome was the proportion of participants who no longer met criteria for a diagnosis of PTSD posttreatment as assessed by a validated instrument. RESULTS: We included 34 randomized clinical trials (N = 3208 participants). Point estimates of diagnosis loss across trauma-focused treatments for nonmilvet samples ranged from 65% to 86%. Milvet samples had lower proportions of diagnosis loss in studies of cognitive processing therapy and prolonged exposure compared to nonmilvet samples, ranging from 44% to 50%. There was substantial overlap between the covariates of milvet status and sex. An exploratory analysis identified eye movement desensitization and reprocessing as having the highest proportion of diagnosis loss, but there was substantial heterogeneity, and none of the studies were milvet-focused or conducted in the US. Also, 95% confidence intervals partially overlapped for all trauma-focused treatment estimates. CONCLUSIONS AND RELEVANCE: This systematic review and meta-analysis contributes to the substantial literature on psychotherapeutic treatments for PTSD by meta-analyzing the probabilities of diagnosis loss for each psychotherapy. Diagnosis loss data are a relatively straightforward way to discuss potential benefits when initiating a therapy or when discussing potential barriers to progress in treatment.